1. Field of the Invention
The present invention relates to a pipe coupling comprising a socket having therein a valve body that opens and closes a fluid passage inside and a plug that moves the valve body in the socket, thereby allowing the fluid passage to open.
2. Description of the Related Art
In general, a pipe coupling of this type is provided with a distal end portion having a plurality of holes arranged at spaces in the circumferential direction, a plurality of lock balls stored in these holes for radial sliding motion, and a sleeve mounted on the outer periphery of the socket for movements in the axial and circumferential directions. This sleeve has a convex pressure surface and concave release surfaces on its inner peripheral surface. It presses the lock balls radially inward by means of the convex pressure surface when it is advanced, and releases the lock balls from the hold by means of the concave release surfaces when it is retreated. Further, the plug includes a distal end portion formed having an engaging groove in which the lock balls can be fitted. When this distal end portion is fitted in the distal end portion of the socket, a valve body in the socket moves to allow a fluid passage to open. As this is done, the lock balls are fitted in the engaging groove, and the sleeve maintains the engagement of the engaging groove and the lock balls.
In the pipe coupling of this type, if a fluid remains in the plug when the socket and plug are to be separated, the plug may possibly jump out under the pressure of the fluid when the socket and the plug are separated. Accordingly, there is a demand for a pipe coupling in which a socket and a plug can be safely separated in a manner such that a fluid in the plug is allowed to be securely discharged before the separation.
Conventionally, one such pipe coupling is described in Jpn. Pat. Appln. KOKAI Publication No. 8-233182, for example.
In this pipe coupling, a lock mechanism that makes a male member immovable in the axial direction causes an urged flap valve, which is mounted in a female member, to open when the male member is temporarily fitted in the female member. A longitudinal claw in a ring-shaped member is caused to engage an annular recess in the body of the male member by the use of elastic means. If a bush moves in the axial direction, the claw is disengaged from the recess, whereupon the male member is released. The female member includes a ring-shaped safety member that has a claw. If the bush is moved in a first axial direction, the male member is made immovable in an intermediate position by means of the claw of the safety member. In this intermediate position, the urged flap valve is closed, and a compressed fluid confined in a lower-stream-side pipe that cooperates with the male member is discharged to the outside. If the bush is moved in a second axial direction that is opposite to the aforesaid direction, moreover, the ring-shaped safety member is controlled so that the male member is released completely.
According to the pipe coupling described above, the construction is complicated, and a large number of components are required. Therefore, the manufacture is troublesome, so that high cost is entailed. Since the bush moves in the two directions, forward and backward, moreover, the overall length increases correspondingly, so that the structure is inevitably bulky.
The object of the present invention is to provide a pipe coupling, which has a simple construction such that its cost and size can be reduced, and in which the pressure of a fluid can be securely removed before. a socket and a plug are separated from each other.
A pipe coupling of the present invention to achieve the above object comprises: a socket including a socket body having a valve body for opening and closing a fluid passage formed therein and a distal end portion having a plurality of holes arranged at spaces in the circumferential direction, a plurality of lock balls stored in the holes for radial sliding motion, and a sleeve fitted on the outer periphery of the socket body, having a convex pressure surface and concave release surfaces on the inner peripheral surface thereof, and adapted to press the lock balls radially inward by means of the convex pressure surface when in an advanced position and to release the lock balls from the hold by means of the concave release surfaces when in a retreated position; and a plug having a distal end portion formed having an engaging groove in which the lock balls can be fitted and adapted to move the valve body to open the fluid passage so that engagement with the socket can be maintained by means of the lock balls in engagement with the engaging groove when the distal end portion is fitted in the distal end portion of the socket, the holes in the distal end portion of the socket including first and second holes individually extending in the axial direction, the first holes extending closer to the distal end side than the second holes, the sleeve being rotatable over the socket body, having convex press extension surfaces extending from the convex pressure surface toward the distal end, and being adapted to press the lock balls on the distal end side of the first holes by means of the convex press extension surfaces when in a given rotating-direction position and to align the lock balls with the concave release surfaces, thereby releasing the lock balls from the hold by means of the convex press extension surfaces, when rotated from the given position, the valve body being adapted to be released from the engagement with the plug and allowed to return to a position such that the fluid passage is closed when the plug is moved away from the socket so that the lock balls in engagement with the engaging groove are located on the extreme distal end side of the first holes.
According to this pipe coupling, if the sleeve is retreated in order to separate the socket and the plug that are connected to each other, the concave release surfaces of the sleeve move onto the lock balls in the second holes, among the lock balls having so far been pressed radially inward by the convex pressure surface of the sleeve and in engagement with the engaging groove of the plug. Thereupon, the lock balls in the second holes are allowed to leave the engaging groove of the plug. On the other hand, the lock balls in the first holes are still pressed radially inward by the convex press extension surfaces, and are in engagement with the engaging groove of the plug. If the plug in this state is pulled in the withdrawal direction, the lock balls in the first holes move, sliding or rolling on the convex press extension surfaces without being disengaged from the engaging groove of the plug. When they reach the distal end side of the first holes, the lock balls prevent the plug from being further drawn out. When the plug is drawn out to this position, the distal end of the plug leaves the built-in valve body in the socket, and the valve body advances to close the fluid passage in the socket, so that fluid remaining in the plug is discharged to the outside through the gap between the socket and the plug. If the sleeve is rotated in the circumferential direction in this state, the concave release surfaces move onto the lock balls in the first holes, thereby allowing the lock balls to leave the engaging groove of the plug. The socket and the plug can be separated from each other by further drawing out the plug in this state.
Preferably, the sleeve is movable in the axial direction only when in the given rotating-direction position and rotatable only when in the advanced position.
According to this arrangement, if the sleeve is retreated in separating the socket and the plug that are connected to each other, the concave release surfaces of the sleeve move onto the lock balls in the second holes, among the lock balls having so far been pressed radially inward by the convex pressure surface of the sleeve and in engagement with the engaging groove of the plug, so that the lock balls are allowed to leave the engaging groove of the plug. On the other hand, the lock balls in the first holes are still pressed radially inward by the convex press extension surfaces, and are in engagement with the engaging groove of the plug. Since the sleeve cannot be rotated in the circumferential direction when in the retreated position, the lock balls in the first holes are still kept pressed radially inward by the convex press extension surfaces, so that the socket and the plug cannot be separated from each other. Further, the sleeve is allowed to rotate if it is moved to the advanced position. If the sleeve is rotated in this position, the concave release surfaces move onto the lock balls in the first holes, so that the lock balls are allowed to leave the engaging groove of the plug, whereupon the socket and the plug can be separated from each other. Thus, in separating the socket and the plug, operation is needed to return the retreated sleeve to the advanced position and rotate it in the circumferential direction in that position. Therefore, the fluid remaining in the plug in the process of this operation is discharged to the outside through the gap between the socket and the plug, so that the socket and the plug can be separated safely.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.